Three-dimensional (3D) inkjet printing is a known process for building three dimensional objects by selectively jetting building materials, for example, photo polymerizable compositions, via ink-jet printing head nozzles onto a printing tray in consecutive layers, according to pre-determined image data. Actinic radiation, for example, ultraviolet (UV) radiation is directed onto the deposited layers of photopolymerizable compositions to solidify or stabilize the layers.
A drawback of 3D printing of UV curable compositions is the tendency of the liquid formulation to solidify on the printing head nozzle plate during the jetting process due to UV reflections, heat or both. Nozzle plate contamination is more severe with compositions containing cationically polymerizable components since cationic polymerization is not inhibited by oxygen and is accelerated by heat. Additionally, once the cationic polymerization mechanism has been initiated, it continues even when not exposed to light. The use of cationic polymerizable compositions is desirable, however, due to certain valuable properties, such as, for example, relatively low shrinkage, high thermal resistance and high chemical and solvent resistance of such compositions.